These studies will provide a data base of detailed and quantified behavioral and neuroanatomical observations pertinent to the hypothesis that neural development is responsive to and normally dependent upon functional activity during embryonic and larval (fetal) stages. Although behavioral and neural development have been clearly demonstrated to depend upon the amount and characteristics of experience and neural function during early postnatal stages, similar data concerning functional effects during the earliest stages of neuro-behavioral development are lacking. Due to this deficiency of experimental data, the developmental role of such a common phenomenon as spontaneous motility, reflecting intrinsic neural activity, is uncertain. Amphibian embryos are anesthetized prior to onset of motility, followed by their release from the anesthetizing agent after various intervals of immobilization. Quantification of motor behavior and sensory-motor responses of these animals are carried out at defined intervals after release. Identical measures are made on normal and control animals. Computer-assisted morphometric analyses of spinal cord elements are also performed on these animals towards the end of gaining insight into the relation of neural activity to cell proliferation and growth, recruitment, competitive interactions, and cell death.